A demand for high-speed and compact design communication systems is mounting as radio LAN, satellite communications, and IMT-2000 advance. Along with this demand, performance increase and compact design are required of elements forming a communication system, such as antenna, filters, amplifiers, etc. Since the antenna is arranged at the front end of a receiver and a transmitter of a system, an increase in radio-wave transmission efficiency and an increase in radio-wave reception gain of the antenna lead to compact design and substantial improvement in communication characteristics of the entire system.
The radio-wave transmission efficiency and the radio-wave reception gain need to be increased. To improve general performance, power loss in high-frequency regions in a conductor portion of a high-frequency device containing an antenna element is preferably reduced. To efficiently increase performance, directivity gain is preferably increased.
The use of a low-resistance superconducting material has been proposed to reduce power loss in high-frequency regions. To realize the idea of using a superconducting material for an antenna device, a heat insulation unit and a cooling unit must be incorporated. The superconducting antenna element needs to be kept at a stabilized cooled state.
An antenna device as an known example 1 is described with reference to FIG. 1. A container of the antenna device of FIG. 1 includes an antenna window 5 and a jacket 6. A window material made of a dielectric material, and having a lens-like configuration in cross section is fitted into the antenna window 5.
The jacket 6 of the antenna device includes an RF connector 1, a cable 2, a micro-strip antenna 3, and a cold stage 4. These elements together with the jacket 6 form the antenna device. The micro-strip antenna 3 is made of a superconducting material.
A vacuum pump is attached to the antenna device. The interior of the jacket 6 of the antenna device is substantially vacuumed, and the micro-strip antenna 3 is heat insulated from the outside while also being cooled by a cold stage 4.
The distance between the antenna window and the micro-strip antenna 3 is set to be a predetermined distance determined by a specific dielectric constant, the thickness and the shape of the lens-like window material fitted into the antenna window 5. (See Patent Document 1.)
Referring to FIG. 2, a stratosphere-mesosphere ozone monitoring system is described. Referring to FIG. 2, there are shown a rotatable dish antenna 408, a λ/4 plate 409 phase shifting a portion of a radio wave received by the dish antenna 408 by a quarter wavelength, a fixed mirror 410 reflecting a radio wave passing through the λ/4 plate, a first oscillator 427, a heat-insulation dewar 429, a waveguide 415, a CGC (cross guide coupler) 416 coupled to the waveguide 415, a SIS (superconductor insulator superconductor) mixer 417, an intermediate-frequency amplifier 418, a cooling load 419, a radiation shield 420, a second oscillator 411, a third oscillator 412, an intermediate-frequency signal processor device 413, an AOS (Acouto-optical Spectrometer) 414, a reference oscillator 424, and a personal computer 425. The elements of FIG. 2, except the second oscillator 411, the third oscillator 412, the AOS 141, the personal computer 425, and the reference oscillator 424, form a main receiver unit 428. The first oscillator includes a frequency multiplier 421, a harmonic mixer 423, a phase-locked controller 426, and a Gunn oscillator 422. (see Non-patent Document 1)
Patent Document 1
Japanese Unexamined Patent Application Publication No. 2003-46325
Non-patent Document 1
Hideo Suzuki et. al. IEICE TRANS. ELECTRON., Vol. E79-C, No. 9, Sep., P 1219–1227, 1996